According to the International Survey of Herbicide Resistant Weeds, the Midsouth accounts for more than 90 of the 160 unique herbicide resistance cases documented nationwide.
“More than half of the resistance cases in the United States are right here in our own backyard and approximately 20 of the more than 90 cases have been documented in rice,” says Ryan Miller, Midsouth market development specialist and new technology specialist, Corteva Agriscienc, Agriculture Division of DowDuPont. “The challenges associated with resistant weed control have created a demand for innovative technology.”
Growers who have struggled controlling troublesome weeds in rice now have a new, effective option to keep fields clean. Loyant herbicide, available this season, brings a new class of chemistry to the rice market with broad-spectrum control of grasses, broadleaves, sedges and aquatic weeds.
Arkansas rice consultant Brent Lassiter says resistance is common in his area, including documented cases of pigweed resistant to ALS, PPO and glyphosate herbicides.
“Resistance management is a big deal and something we’ve been dealing with for a long time,” Lassiter says. “Pigweed is especially robust and adaptive to its climate. ALS resistance is increasingly a challenge for rice growers. ALS-resistant flatsedge is becoming a real issue, as is tough-to-control nutsedge, barnyardgrass and other grasses.”
Loyant herbicide with Rinskor active brings a new class of chemistry, controlling ALS-, glyphosate-, ACCase-, PPO- and triazine-resistant biotypes as well as other Group 4-resistant weeds in rice.
“Rinskor active, the new active ingredient in Loyant, has an alternative binding site from other Group 4 herbicides,” Miller says. “That means it is able to control not only susceptible species but also species with resistance to Group 4 herbicides such as quinclorac.”
Cost of resistance
The evolution of resistance has significantly increased rice production inputs and associated costs.
“Rice growers can spend more than twice as much as corn and soybean growers on an effective herbicide program,” Miller says.
Barnyardgrass is one of the most troublesome weeds in rice. According to research by University of Arkansas Extension, heavy barnyardgrass infestation in rice can result in a yield reduction of 30 percent to complete crop loss. In the Midsouth, it’s not uncommon to find barnyardgrass that is resistant to multiple chemistries in a single production field.
“Utilize multiple effective modes of action to prevent herbicide resistance and protect current technologies,” Miller says. “Loyant provides an effective mode of action on resistant sedges, broadleaves, aquatics and grasses, including multiresistant barnyardgrass.”